Mine did something similar when I first got it.

It was the vnt mechanism on the turbo sticking closed resulting in underboost.

A few hard drives later, and its freed up.

It's possible to clean the mechanism with my muscle if it's really sooted up

We had an intercooler pipe failure on our old Ibiza 130 PD....the splines that kept it snapped into place when twisted on broke off so under acceleration as soon as the boost came in the pipe would pop off....it then sounded like a tank, ran like crap and smoked like anything.....essentially the car was venting all its boost and lost all back pressure.

It was on its way out but whilst diagnosing the issue the dealership.finished the pipe off....wife left the dealership just around 18:00hrs and popped off immediately...she then drove the thing all the way home!

The garage had to recover it and fit a new IC pipe then it was fine.

I only mention it as it could be your IC pipe is on its way out as he problem was intermittent on ours until the dealership trashed the pipe....under normal driving it tended to be fine but as soon as you put the car under some heavy load (acceleration) it would play up.

Edited 11 October, 201510 yr by pipsypreturns